My priorities, possibly not exhaustive

1) be able to have sensible discussions about the encodings of literals in
the standard

2) use the same terminology we would use in describing Library facilities
today

3) fix the hand waving in raw literals and any other place that in practice
compilers access the logical source file.

4) be able to avoid "standard" terms that aren't actually in the standard,
such as 'execution encoding', by having actual terminology.

5) remove the conversion to universal-character-name while keeping that as
an escape sequence. Use notional code points instead, which cleans up
accidentally forming a ucn.